Known pet toilet systems for treating the excreta of pets such as cats and dogs include those disclosed in JP 7-67489A and JP 2003-180182A, in which a toilet box is partitioned into upper and lower compartments by a foraminous member (drainboard), with an excreta treating material put in the upper compartment and a urine absorbent member made of an absorbent polymer, plant fiber, pulp, etc. set in the lower compartment.
According to these pet toilet systems, liquid waste discharged by a pet animal is allowed to quickly pass the excreta treating material placed in the upper compartment, drop through the drain holes of the drainboard, and be positively absorbed by an urine absorbent member, such as a urine absorbing mat, laid in the lower compartment of the toilet box. The excreta treating material is exemplified by litter obtained by heat compressing a ground material comprising softwood sawdust into pellets that self-disintegrate upon water absorption (see JP 9-308403A).
JP 2002-84909A discloses a technique of an excreta treating material prepared by molding a combination of a ground material of plant origin and a synthetic resin into pellets having sufficient shape retention so as not to disintegrate upon water absorption. The technique is established by designing a dusting ratio at 5% or less and a water absorption rate at 10% or less when immersed in 25° C. water for five seconds.